Question

∠A与∠DCB有怎样的关系?

Answer 1

AC=AD,∠DCA=∠CDA

∠A+∠DCA+∠CDA=180°

∠A=180°-2∠DCA

∠ACB=90°

∠DCB=90°-∠DCA

=1/2（180°-2∠DCA)

=1/2∠A